Sleep is important for good health. Frequent disturbances during sleep or sleep fragmentation can have severe consequences including day-time sleepiness (with the attendant possibility of motor-vehicle accidents), poor mentation, memory problems, depression and hypertension. For example, a person with nasal congestion may snore to a point that it disturbs that person's ability to sleep. Similarly, people with OSA are also likely to disturb their partner's sleep. The best form of treatment for patients with OSA is continuous positive airway pressure (CPAP) applied by a flow generator such as a blower (compressor) via a connecting delivery hose with a patient interface. The positive pressure can prevent a collapse of the patient's airway during inspiration, thus preventing events such as snoring, apnoeas or hypopnoeas and their sequelae.
Such positive airway pressure may be delivered in many forms. For example, a positive pressure level may be maintained across the inspiratory and expiratory levels of the patient's breathing cycle at an approximately constant level. Alternatively, pressure levels may be adjusted to change synchronously with the patient's breathing cycle. For example, pressure may be set at one level during inspiration and another lower level during expiration for patient comfort. Such a pressure treatment system may be referred to as bi-level. Alternatively, the pressure levels may be continuously adjusted to smoothly replicate changes in the patient's breathing cycle. A pressure setting during expiration lower than inspiration may generally be referred to as expiratory pressure relief. As described by Sullivan in U.S. Pat. No. 4,944,310, positive airway pressure treatments typically provide gas under pressures to the patient in the range of 4 to 15 cmH2O from the device and may involve flow rates of at about 120 liters/minute. Some of the air will escape via an end restriction and not be delivered to the patient. These pressure settings may also be adjusted based on the detection of conditions of the patient's airway. For example, treatment pressure may be increased in the detection of partial obstruction, apnea or snoring.
Other devices are known for providing respiratory tract therapy. For example, Schroeder et al. describes an apparatus for delivering heated and humidified air to the respiratory tract of a human patient in U.S. Pat. No. 7,314,046, which was filed on 8 Dec. 2000 and assigned to Vapotherm Inc. Similarly, Genger et al. discloses an anti-snoring device with a compressor and a nasal air cannula in U.S. Pat. No. 7,080,645, filed 21 Jul. 2003 and assigned to Seleon GmbH.
Respiratory treatment apparatus are sometimes provided with accessory components for comfort conditioning of the flow or pressurized air supplied by the flow generator. For example, the supplied air may be applied to a humidifier to humidify and warm the treatment gas prior to its delivery to a patient. Similarly, various heating elements can be connected with a delivery conduit to help in maintaining a particular temperature of the supplied gas as it is conducted to the patient from a supply unit or humidifier.
These elements can place a significant demand for power during operations of the device. It may be desirable to develop these devices for treating upper respiratory conditions with improved design efficiencies.